1. Field of the Invention
The present invention relates to a mounter head for a surface mounting apparatus which is capable of easily controlling a pitch of the surface mounting apparatus as well as preventing backlash when the apparatus is mounted on a printed circuit board.
2. Description of the Prior Art
Electric and electronic products have been developing rapidly with high density, small size and variety. Development of surface mounting technology using a surface mounting apparatus for manufacturing a Printed Circuit Board (PCB) has also developed rapidly.
The surface mounting apparatus is a very important component of the surface mounting assembly apparatus for mounting a surface mounting device to the PCB and is supplied with the surface mounting device from a device supplier, which feeds it to a mounting position on the PCB and mounts it on the PCB.
The surface mounting apparatus can be divided by function into high-speed apparatus and general-use apparatus. The high-speed apparatus can accomplish a high-speed mounting operation because it is constructed to assemble many devices in a short period of time. Therefore, it has the advantage that it can be utilized for mass production. However, its mounting precision may be reduced.
Meanwhile, the general-use apparatus can accomplish a high-precision mounting operation because it is constructed to function with many devices. Therefore, it has the advantage that it can be utilized for medium or small production. However, productivity may be reduced because of the low-speed mounting operation.
A surface mounting apparatus comprises a feeder (referring to xe2x80x9ca tape feederxe2x80x9d as below) for supplying a device to be mounted, an X-Y gentry for determining a working position, a conveyor for carrying a PCB and a head for picking up, in regular sequence, a device from the feeder and for mounting the device on the PCB. In general, the surface mounting apparatus serves to mount an electronic device on the PCB and can be called a mounter. More detailed structure for the mounter is as follows.
The mounter comprises a base assay, a conveyor installed at an upper portion of the base assay for feeding a PCB, a feeder for supplying a device or a chip to be mounted on the PCB, a mounter head assay for mounting each device supplied from the feeder, a vision part for acknowledging and correcting the position of the device, and an X-Y gentry installed with the vision part and the mounter head for determining the position of the table.
Meanwhile, the mounter head assay comprises driving means for driving the mounter head, a suction nozzle for directly sucking the device, nozzle fixing means for fixing the sucked device, and a nozzle exchanging apparatus for exchanging the nozzle.
The mounter head is constructed to rotate about a R-axis 360 degrees, as shown by arrow R in FIG. 1, to control the rotation angle of the device sucked by the nozzle and along a Z-axis, as shown by arrow Z in FIG. 1, for moving up and down to suck the device by the nozzle The suction nozzle of the mounter head is installed on the nozzle shaft and is rotatable by 360 degrees. The nozzle shaft is rotated on the R-axis by the driving means and is moved up and down on the Z-axis by the pinion and the rack by other driving means.
However, the conventional mounter head provides one driving means for rotation pf each of the nozzle shafts about the R-axis. Each nozzle shaft is rotated about the R-axis after the driving motor is connected to the nozzle shaft by a belt. That is, although the first nozzle shaft, which is connected to the driving means correctly receives the rotation angle from the driving means, errors often occur in the rotation of the second, third, and fourth nozzles due to backlash caused by belt slip and the distance between the respective nozzle and the belt. Therefore, the rotating angle of the nozzle shaft can be precisely controlled, thereby causing the device not to be correctly sucked or mounted when the surface mounting device is mounted on the PCB.
Therefore, the conventional surface mounting apparatus has the problem of inefficient mounting and the device thus may not work properly.
Further, the surface mounting device can be divided into a semiconductor device being supplied from a tape feeder and a semiconductor devices being supplied from a tray feeder.
That is, in case of a semiconductor device supplied from a tape feeder, the surface mounting device is supplied with devices from supply rolls. Each roll is disposed at a predetermined distance therefrom, thereby having the same pitch. Accordingly, each nozzle can suck only one device at a time.
FIG. 1 shows the structure of a mounter head of a conventional surface mounting apparatus filed by Yamaha in Japan and issued as U.S. Pat. No. 5,377,405. The surface mounting apparatus of FIG. 1 comprises a carriage, a plurality of picker device 124, sensing means 122, and a driving source 120.
The surface mounting apparatus having the above construction is operated so that the sensing means 122 senses the devices so as to simultaneously pick up the electronic devices. However, in the conventional apparatus, driving means and peripheral apparatus for moving the mounter head are not provided. That is, each mounter head is constructed to be simultaneously moved by the driving source 120. Therefore, the conventional nozzle installed at the mounter head simultaneously moves corresponding to the pitch of the surface mounting device supplied to the feeder. However, in the case of a tray feeder in which the device size inserted therein to is different, respectively, a small device inserted into the tray may have a narrow pitch. Further, because a larger-sized device has a wider pitch it is very difficult to suck the device using the conventional nozzle.
Because the nozzle is designed to have the same pitch, it works well with a supply of same pitch devices. However, productivity deteriorates when devices having a different pitch device are supplied.
Accordingly, the present invention has been invented to solve the above problems and it is an object of the present invention to provide a mounter head for a surface mounting apparatus in which the precision of the R-axis rotation is increased by providing a driving means for rotating the nozzle shaft so that the device is correctly sucked and mounted.
Another object of the present invention is to provide a mounter head for a surface mounting apparatus which is capable of being applied to a tray feeder having therein a supply of same pitch devices, as well as to a tray feeder having therein a supply of devices each having a different pitch.
To accomplish the above objects, the present invention provides a mounter head for a surface mounting apparatus comprising a rack block having a rack which is movable up and down by a pinion rotated by a driving source, a nozzle shaft installed at one side of a moving means, a nozzle secured to a lower end of the nozzle shaft for sucking a device to be mounter, and a driving source installed corresponding to each nozzle shaft for rotating each nozzle.